There is huge variation in fuel efficiency between transatlantic airlines, with British Airways and Lufthansa emitting 51% more carbon dioxide than the cleanest flyers, according to a report by the organisation that revealed the VW test-rigging scandal.

Pollution from a non-stop transatlantic round trip averages around one tonne of CO2 per passenger, the International Council on Clean Transportation (ICCT) research found – the same as would be clocked up in a year by commuting 22 miles to work daily in a Toyota Prius.

Separately, a leaked European parliament study seen by the Guardian has forecast that the aviation and shipping industries will make up 39% of global CO2 emissions by 2050, based on present trends.

The ICCT report said a typical passenger on Norwegian Air Shuttle travelled 40km per litre of fuel, while flyers on British Airways and Lufthansa travelled only 27km.

Dan Rutherford, an author of the report, said: “Eighty per cent of the difference can be explained by two factors: seating configurations – how much premium, business and first-class seating you have – and the fuel burn of an aircraft, or how efficient it is. Norwegian Air Shuttle has invested more in newer, more fuel-efficient planes, while BA is using older, predominantly 747 aircraft.”

First-class and business passengers accounted for a disproportionate amount of the pollution. Premium passengers were responsible for 14% of available seat kilometres flown on transatlantic routes, but they accounted for around one-third of total carbon emissions, the paper found.

Other poor performers in the study included United Airlines, Virgin Atlantic and American Airlines, who scored barely above BA and Lufthansa. At the other end of the table, Air Berlin, KLM and Aer Lingus averaged 36km per litre of fuel.

Rutherford said the results, which will be filed with the International Civil Aviation Organisation (Icao), showed a deterioration from last year’s rankings, which revealed a 25% difference between best and worst performers.

“There is a large and underestimated potential for in-sector CO2 emission reductions,” the report states. “This highlights the role for additional policies to limit aviation emissions, notably the CO2 standard being developed by the Icao and a global market-based measure to price aviation carbon.”

International airlines and shipping companies are not currently obliged to cut their CO2 output. An attempt to include aviation in the EU’s emissions trading system was defeated two years ago. Icao says it will try for carbon neutral growth after 2020, but expects no new policies before an assembly in November 2016.

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The projections in the leaked European parliament study suggest that aviation and shipping will continue to increase their share of global emissions. It predicts that by 2050 aviation will account for 22% of the total, and shipping 17%.

“Clearly this would derail the efforts in Paris to stay within two degrees’ warming,” said Sotiris Raptis, a shipping policy officer at Transport & Environment. “Any deal in Paris must lead to an emissions reduction target for aviation and shipping, like all other sectors of the global economy.”

Airline emissions are currently responsible for an estimated 5% of global warming, and the shipping industry around half that, and both figures are growing fast. Globally, aircraft emitted about 700m metric tonnes of CO2 in 2013, and without policy intervention that figure is expected to triple by 2050.

The issue will be discussed at the Paris climate summit, after an attempt to remove it from the draft text was blocked.